I was traumatized by the ferry ride from Koh Tao to Surat Thani. Though the ticket was a well-haggled 800 THB inclusive of ferry from
Koh Tao to Surat Thani, bus from Surat Thani to Krabi, and ferry from Krabi to Koh Phi Phi Don.
We weren't given seats but beds since it was a ten-hour overnight trip. Had it been a day trip, it would just be five hours via express boat. The water was rough and I felt the boat crashing into the waves one after the other. I have never felt so sea sick in my whole life!
For this overnight ride, passengers are given beds, not seats.